The invention concerns a lever-type cam follower made of thin-walled material like sheet metal, particularly for a valve train of an internal combustion engine, comprising two parallel side walls connected by a crossbeam, an underside of the crossbeam having at one end, a separate securing element comprising two cheeks that are parallel to the side walls for laterally guiding a gas exchange valve the crossbeam comprising an aperture having a crossbar oriented toward the securing element.
DE-OS 197 30 201 discloses a cam follower of the pre-cited type that is considered to be generic. This cam follower is likewise made of a sheet metal and possesses at one end, a separate securing element for a lateral guidance of a gas exchange valve. This securing element is configured as a U-like clip which is placed with its crossbar over side walls of the cam follower. A drawback of this prior art is that for guiding the securing element, the side walls of the cam follower are recessed. On the one hand, this weakens the cam follower in this region and on the other hand, manufacturing work and costs are unnecessarily increased.
U.S. Pat. No. 5,016,582 discloses a sheet metal cam follower of a related type whose valve stem support is made on one end by a complex bending design. Due to the doubling of the cam follower resulting from bending, on the one hand, the mass moment of inertia of the cam follower is unnecessarily increased. On the other hand, a relatively great amount of manufacturing work is required for obtaining the aforesaid doubling which is accompanied by the risk of crack formation and the like.
The object of the invention is therefore to create a cam follower of the pre-cited type in which the mentioned drawbacks are eliminated by simple means.
The invention relates to a lever-type cam follower (1) made of thin-walled material like sheet metal, particularly for a valve train of an internal combustion engine, comprising two parallel side walls (2) connected by a crossbeam (3), an underside (10) of the crossbeam (3) having at one end (5), a separate securing element (6) comprising two cheeks (16) that are parallel to the side walls (2) for laterally guiding a gas exchange valve, the crossbeam (3) comprising an aperture (13) having a crossbar (12) oriented toward the securing element (6), wherein the securing element (6) has a U-like geometry in which a web (9) that connects opposing legs (7, 8) of the securing element (6) bears against the underside (10) of the crossbeam (3) and comprises an opening (11) in which the gas exchange valve can be guided, the cheeks (16) are formed on the opening (11), and as viewed in a longitudinal direction of the cam follower (1), the legs (7, 8) are situated behind one another, one leg (7) extending into the aperture (13) is retained on the crossbar (12) and the other leg (8) is retained in the region of an end (14) of the cam follower (1) on the one end (5).
According to this claim, the securing element has a U-like geometry in which a web that connects opposing legs of the securing element bears against the underside of the crossbeam and comprises an opening in which the gas exchange valve can be guided, the cheeks are formed on the opening, and as viewed in a longitudinal direction of the cam follower, the legs are situated behind one another, one leg extending into the aperture is retained on the crossbar and the other leg is retained in the region of an end of the cam follower on the one end.
Further advantageous features of the invention are the subject matter of the subclaims each of which can contain independently patentable measures in itself or in combination with others.
The securing element of the invention enables cam followers with prior art configurations to be used. It must be noted that there is no weakening of the cross-section of the cam follower in the region of the securing element. The securing element is simple and cheap to manufacture and it can be fixed through its legs on an upper surface of the crossbeam for example by clipping, bending, snapping or crimping. The lateral guidance on the gas exchange valve is realized solely by edges of an opening punched out of the web of the securing element.
If an additional guide height is desired, according to a further feature of the invention, the region of the lateral cheeks of the opening can be raised compared to the height of the opening itself. The cheeks can then be made, for example, out of the material that was originally a part of the opening.
A securing element, particularly rigid in the region of guidance, is obtained if the entire opening is formed with an extension extending away from the web, which extension then comprises the cheeks. Advantageously, this extension has the same height around its entire periphery.
In a further preferred configuration of the invention, at least one of the legs of the securing element comprises a window into which the crossbeam extends. In this way, the securing element in its turn is very simply fixed on the crossbeam. It is, however, also conceivable and provided for by the invention to bend at least one of the legs in the manner of a hinge onto the upper surface of the crossbeam.
If the securing element is to be connected to the crossbar by crimping the legs, it can be given a soft configuration at least in its leg region so that crimping can be effected in an uncomplicated manner. At the other endd, the securing element can also have a springy configuration which enables it to be connected to the crossbeam in a simple manner by clipping.
The U-profile of the cam follower proposed in a further sub-claim, in which an underside of the crossbeam of the cam follower is oriented away from the side walls, results in a particularly rigid configuration of the cam follower. However, an inverted U-profile, an H-profile or the like is also conceivable. The scope of the invention likewise extends to a cam follower that is not made of steel sheet but of a light-weight material or a composite material, or of cast metal and the like.
The roller in the aperture of the crossbeam that is held in the side walls of the cam follower minimizes work consumed by friction in the valve train, but a sliding contact is also conceivable.
It is also a subject matter of the invention to make a gap between the roller and the adjacent leg of the securing element smaller than (or, at the most, of equal dimension to) a thickness of the leg. This creates an excellent security against a possible tendency of the securing element to jump off during operation. At all events, the gap must be so small that, if an undesired jumping-off does take place (caused by an acceleration jerk etc.), the leg is retained by positive engagement on the roller.
Advantageously, the cam follower is configured as a finger lever that is mounted on its other end on a support element. However, the invention applies to all kinds of lever-type cam followers having a securing element that may be used in a valve train of an internal combustion engine and for which it is desired to realize an extremely simply structured guidance on at least one gas exchange valve.